1. Field of the Invention
The present invention relates to communication networks including as plurality of small cells. More particularly, the invention relates to the management of small cell communication and call control in a Heterogeneous Network (HETNET).
2. Description of the Prior Art
Long-Term Evolution (LTE) is a standard for wireless communications. The standard was developed by the 3rd Generation Partnership Project (3GPP). The original standard is referred to as Release 8 and a follow-on with minor enhancements is referred to as Release 9. An aspect of Release 8 was the introduction of Circuit Switch Fallback (CSFB). CSFB provides the voice and messaging delivery to LTE devices, such as mobile phones, for example, through a circuit-switched network, such as global system for mobile communications (GSM), for example. CSFB is used in circuit-switched operations that arrive over LTE networks, which are packet-based. That is, CSFB is useful in HETNETs. The fallback is to enable signal exchange where older 2G or 3G functionality exist for a mobile device. The enhanced version of CSFB (eCSFB) established in Release 9 resolved some undesirable aspects of Release 8 CSFB including, for example, latency problems.
An example existing HETNET with eCSFB is shown in FIG. 1. Characteristics of CSFB and eCSFB are as follows.
3GPP Release 8 CSFB
                Request for Circuit Switched (CS) services (Mobile Originated (MO) and Mobile Terminated (MT)) are handled via Internetworking Function (IWF)        LTE Evolved Packet System (EPS) supports CSFB by releasing Radio Resource Control (RRC) Connection and redirection to 1× Radio Transmission Technology or CDMA2000 1× (IS-2000) (1×RTT, which is a data transmission system used on Code Division Multiple Access (CDMA) networks that allows for connection speeds up to 144 kbps        Pre-registration support for 1×RTT necessary; enabled via System Information Broadcast (SIB) 8 and tunneling of 1×RTT messages3GPP Release 9 eCSFB        Requires R9 User Equipment (UE), Mobile Management Entity (MME), Mobile Switching Center (MSC) and evolved Node B (eNB) support.        Reduce Latency in 1×CSFB                    Enables tunneled messages between 3GPP's LTE air interface Evolved Universal Terrestrial Radio Access Network (EUTRAN) and 1×RTT            Reduces CS voice call set up time by handover preparation and pre-assigning CDMA Channel                        Enables concurrent High Rate Packet Data (HRPD) Public Safety (PS) Handover        Supports Dual Rx 1×CSFB                    Pre-registration not required. UE maintains 1×RTT context and re-registrations There may be some challenges associated with facilitating eCSFB in LTE HETNETs incorporating small cells, often referred to as femto cells, as follows.                        Current Session Initiation Protocol (SIP) based Convergence Server (CS) needs to be upgraded to interface with 1×CS IWS A interface Destination 1×FAP Identification Issue        1×CS Internetworking Server (IWS) needs to obtain Pseudo Noise (PN)-1×Base Station (BS) Femtocell Access Point (FAP) Identification Mapping (“Inter-Radio Access Technologies (RAT) Neighbor Relation Table (NRT)”        Multiple 1×RTT FAPs may share common PN        Pilot Measurement with PN information/identification is not sufficient to identify 1×RTT BS/FAP3GPP Release 8 CSFB        Request for Circuit Switched (CS) services (Mobile Originated (MO) and Mobile Terminated (MT)) are handled via Internetworking Function (IWF)        LTE Evolved Packet System (EPS) supports CSFB by releasing Radio Resource Control (RRC) Connection and redirection to 1×RTT, which is a data transmission system used on Code Division Multiple Access (CDMA) networks that allows for connection speeds up to 144 kbps        Pre-registration support for 1×RTT necessary; enabled via SIB 8 and tunneling of 1×RTT messages        
3GPP Release 9 eCSFB                Requires R9 User Equipment (UE), Mobile Management Entity (MME), Mobile Switching Center (MSC) and evolved Node B (eNB) support.        
What is needed is an Improved way to enable eCSFB in HETNETs.